Florida’s Department of Corrections’ Inspector General’s office announced Friday it is reopening an investigation into the death of Darren Rainey, a mentally ill inmate who was left in a scalding shower by guards for almost two hours at Dade Correctional Institution in June 2012.

The move came on the same day the Miami Herald filed a lawsuit against the agency in an effort to get access to public documents that DOC had refused to release in connection with his death.

Part of the newspaper’s legal argument for releasing the documents was that the IG had closed its probe into the death two years ago and therefore, what actions, if any, the agency did to investigate the death should be open to public scrutiny.

Reopening the probe also came on the same day that DOC Secretary Michael Crews announced that the agency will conduct a review into the way it treats mentally ill prisoners.

“The Department will build upon the existing training and resources staff has received to help them recognize mental illness...and to de-escalate incidents without force being necessary,’’ Crews said in a written statement.

But Howard Simon, executive director of the American Civil Liberties Union of Florida, said that isn’t enough.

“That’s great, they are going to look at their practices, but who is going to be held accountable for the death of Darren Rainey?’’ Simon said.

“Somebody died a horrible death in a correctional institution, and where is the report on what happened?’’

The actions follow a Herald investigation into the scalding death of 50-year-old Rainey, who was, according to inmate witnesses, locked in a closet-size shower after defecating in his cell. The guards controlled the shower temperature on the outside. Water temperatures in the shower were measured later and topped out at 180 degrees, one inmate said.

Harold Hempstead, an inmate who worked as an orderly in the psych unit, told the Herald — and the Inspector General’s office in a series of grievances — that corrections officers had used the shower before as a means to control inmates. He also said Rainey begged and cried for help as he was left there unattended.

Two other inmates individually wrote to the department, one saying he was orderd to clean up the “crime scene,” the other saying Rainey was slapped and punched on the way to the shower.

When Rainey was found, he was dead and his skin had separated from his body.

A number of other inmates and former medical staffers at the prison have alleged to the Herald and in grievances and in a suicide note that corrections officers at state prison south of Homestead routinely mistreated mentally ill inmates and, in some cases, physically and sexually tormented them, as well as making them fight for the entertainment of staff.

DCI is one of six state prisons in Florida that have transitional care units to house mentally ill inmates.

The prison system and law enforcement authorities have come under criticism for failing to conduct a full investigation of Rainey’s death when it happened.

To date, no one has been disciplined or charged. Miami-Dade police conducted interviews of witnesses only after the newspaper began asking questions about the case last month. The Miami-Dade medical examiner has declined to release Rainey’s autopsy report.

In a letter to Crews Friday, DOC Inspector General Jeffrey T. Beasley said investigators would proceed with an “internal review of portions of the incident’’ concerning the “construction, operation and maintenance’’ of what he called the “shower/decontamination cell’’ at DCI.

Beasley also said DOC’s health and safety team would perform statewide inspections of all prison showers to ensure their proper and safe operation.

Crews on Friday did not mention Rainey.

Rainey’s brother, Andre Chapman, has never been contacted by anyone from the agency other than the prison’s chaplain, who told him about his brother’s death two years ago. Rainey’s death certificate does not have a cause of death even though Medical Examiner Bruce Hyma said the autopsy was conducted 18 months ago.

Rainey was serving a two-year prison term for cocaine possession. He was scheduled to be released this July.

“When you look at his underlying offense — possession of cocaine with intent to distribute — I don’t think torture and death should be part of the punishment for that offense,’’ said state Rep. Katie Edwards, a Broward County Democrat.

Earlier this week, Edwards wrote to the DOC’s legislative liaison, Will Kendrick, demanding that the prison system’s leaders be held accountable for “their lack of leadership and honesty with the Legislature and the public.’’